Spreading and lap-forming machine

ABSTRACT

A web of fibers (4) is conveyed by conveyor-belts (2, 5) which pass around rollers (32 to 43, 60 to 69). Some of these rollers are carried by main carriages (10, 14) which are capable of displacement in reciprocating motion above an apron (8) which moves in a direction parallel to the axes of the rollers and collects the web (4) in the form of a lap. Auxiliary carriages (16, 18) are provided for maintaining the length of the paths of the conveyor-belts (2, 5) at a constant value in spite of the reciprocating movements of the main carriages (10, 14). Each auxiliary carriage (16, 18) is located within a bottom passageway (70) which extends beneath the apron (8) and is separated from the apron by at least one partition-wall (72). 
     The invention is applicable to the manufacture of nonwoven fabrics.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spreading and lap-forming machine forconverting a web to a lap by folding in pleats.

2. Description of the Prior Art

In a machine of this type as disclosed, for example, in patent documentFR-B-2,553,102, a web delivered by a card is first conveyed by a firstconveyor-belt or so-called front belt to a pinching zone in which it ismaintained between the first belt and a second belt and conveyed to anoutput carriage. The reciprocating motion of the output carriage above areceiving apron causes deposition of the web which said carriagedischarges onto the apron in alternate accordion pleats. Since the apronmoves in a direction parallel to the axes of the guide rollers carriedby the output carriage, the successive pleats are relatively displacedalong this direction and the web thus forms on the apron a continuouslap, the lateral edges of which are defined by the pleats. The beginningof the pinching zone is defined as a position in motion by an inputcarriage which performs a reciprocating movement. This movement isintended to ensure that the speed of admission of the web into thespreading machine is made compatible with the speed of unwinding of theweb by the output carriage in spite of the reciprocating movements ofsaid carriage. Thus the web, which has a fragile structure, is notdisturbed either by packing or by stretching or by friction.

In machines of this type, the developed length of the closed pathsfollowed by the conveyor-belts must be maintained constant in spite ofthe reciprocating movements of the carriages.

In some designs, the reciprocating motion of the input carriage iscompensated by the contrary reciprocating motion of the output carriageand conversely by means of a suitable arrangement of the guide rollers(reference can be made, for example, to patent document FR-B-2,553,102).

In other designs (see FR-B-2,234, 395, U.S. Pat. No. 1,886,919 orFR-A-2,373,095), provision is made for one or a number of auxiliarycarriages which also carry out reciprocating movements of translation inorder to selectively lengthen or shorten the conveyor-belts outside thepinching zone and thus to compensate for variations in length of thepinching zone.

The present Application is more particularly concerned with this secondtype of construction.

It has been found that spreading and lap-forming machines of this typegive rise to difficulties when they operate at the high speeds which maybe desired in order to increase production rates. The alternating motionof the auxiliary carriages in that case produces relatively violent aircurrents which tend to disperse the web conveyed on the front beltupstream of the input carriage. This may result in defects inhomogeneity of the lap produced and even in jamming of the web in thepinching zone.

In the spreading and lap-forming device described in patent documentU.S. Pat. No. 1,886,919, the auxiliary carriages are slidably mountedwithin the closed loop described by the apron which receives the lap.Their reciprocating movements therefore produce air currents in thevicinity of the lap deposited on the apron, with the result that thisspreading and lap-forming device cannot produce a uniform lap atrelatively high speeds.

In the spreading and lap-forming device described in patent documentFR-A-2,373,095, the auxiliary carriage moves above the input carriage.This structure reduces the disturbing effect of the movement of theauxiliary carriage on the formed lap in comparison with U.S. Pat. No.1,886,919. However, this disturbing effect is in fact exerted on the webwhich is supplied to the input of the machine. This results in the samedisadvantage: uniformity of the lap formed at the exit of the spreadingmachine is poor, particularly at high speed.

One of the objects of the present invention is to solve thesedifficulties and to provide a spreading and lap-forming machine whichproduces a uniform lap, even at high speed.

SUMMARY OF THE INVENTION

The spreading and lap-forming machine in accordance with the presentinvention comprises two conveyor-belts which are each intended to followa closed path and are associated with rollers for respective guiding anddisplacement of said conveyor-belts, the closed paths being external toeach other and adjacent to each other in a pinching zone delimited byguide rollers carried by two main carriages which are capable ofdisplacement in translational motion in a horizontal direction at rightangles to the axes of the rollers, compensating means including at leastone auxiliary carriage which is capable of displacement in translationalmotion at right angles to the axes of the rollers so as to maintain thelength of each closed path at a substantially constant value, eachclosed path being intended to make a 180-degree turn around at least oneguide roller carried by an auxiliary carriage, means for bringing theweb to the entrance of the pinching zone, an apron which is capable ofmoving in a direction parallel to the axes of the rollers and receivesthe web as it passes out of the pinching zone, and driving means forapplying reciprocating movements of translation to the main carriagesand to the compensating means.

In accordance with the invention, said spreading and lap-forming machineis distinguished by the fact that each auxiliary carriage is locatedwithin a bottom passageway which extends beneath the apron and isseparated therefrom by means such as a partition-wall whereby aircurrents generated in particular by the auxiliary carriages areprevented from propagating to the web and/or the lap which is beingformed.

By virtue of this arrangement, the air currents produced by thereciprocating motion of the auxiliary carriages fail to reach the levelof the web or of the lap or at least reach them in a substantiallyattenuated state since they remain essentially confined to the interiorof the bottom passageway. In consequence, these movements practically donot affect the regularity of transfer of the web and the formed laptherefore has improved homogeneity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external view in perspective showing a spreading andlap-forming machine.

FIGS. 2 to 4 are schematic views in elevation showing a spreading andlap-forming machine in accordance with the invention in three differentpositions.

FIG. 5 is a view in elevation to a larger scale showing in greaterdetail the input carriage of the spreading and lap-forming machine ofFIGS. 2 to 4.

FIG. 6 is a plan view taken along the plane VI--VI indicated in FIGS. 4and 7.

FIG. 7 is a partial plan view taken along the plane VII--VII indicatedin FIGS. 4 and 6.

FIG. 8 is a view which is similar to FIG. 5 and shows the outputcarriage of the spreading and lap-forming machine.

DETAILED DESCRIPTION OF THE INVENTION

The spreading and lap-forming machine shown in perspective in FIG. 1includes a first conveyor-belt 2 or so-called front belt which collectsthe web of fibers 4 delivered for example by a card (not shown) andconveys it into the enclosure 1 in which it is converted by folding to alap 6, said lap being conveyed by an apron 8 to the exterior of theenclosure 1. The apron 8 conveys the formed lap 6, for example to aneedle-punching unit (not shown). The directions of conveyance of theweb 4 and of the lap 6 are respectively indicated in FIG. 1 by thearrows F and K. For reference purposes, the expression "front side" ofthe spreading and lap-forming unit will designate the side 7 adjacent tothe face through which the web 4 is admitted and the "rear side" of thespreading and lap-forming unit will designate the side 9 opposite to thefront side 7.

The interior of the spreading and lap-forming machine is illustratedschematically in the views in elevation of FIGS. 2 to 4, these viewsbeing taken along a plane Q perpendicular to the direction of conveyanceof the lap 6 by the apron 8.

The spreading and lap-forming machine includes a second conveyor-belt 5or so-called rear belt which is associated with the front belt 2. Thebelts 2 and 5 shown in full lines in FIGS. 2 to 4 have the same widthand their lateral edges are located in the same planes parallel to theplane of FIGS. 2 to 4. The front belt 2 follows a closed path made up ofsections 20 to 31 delimited by cylindrical guide rollers 32 to 43. Therear belt 5 follows a closed path made up of sections 50 to 59 delimitedby cylindrical guide rollers 60 to 69.

The guide rollers 32 to 43, 60 to 69 are pivotally mounted aboutrespective axes which are perpendicular to the plane of FIGS. 2 to 4 orin other words parallel to the direction of motion of the apron 8. Theshafts of the rollers 32, 33, 39, 40, 42, 43 and 65, 66, 68, 69 arestationary with respect to the frame 1 of the spreading and lap-formingmachine. The shafts of the rollers 34, 35 and 60, 61, 62, 63 are carriedby a first main moving carriage 10 or so-called input carriage. Theshafts of the rollers 36, 37, 38 and 64 are carried by a second mainmoving carriage 14 or so-called output carriage and the shafts of therollers 41 and 67 are carried by auxiliary carriages 16, 18.

For each closed path 20 to 31, 50 to 59 of the conveyor-belts, anauxiliary moving carriage 16, 18 carries a guide roller 41, 67 aboutwhich said closed path makes a turn through an angle of 180 degrees. Thetwo auxiliary carriages 16, 18 have movements which compensate those ofthe main carriages 10, 14 so as to maintain substantially constant thelength of each of the closed paths 20 to 31, 50 to 59.

In the case of each conveyor-belt 2, 5, at least one of thestationary-shaft rollers (for example the rollers numbered respectively39 and 65) is driven in rotation by known means (not shown) so as tocause the belts 2, 5 to travel along their respective closed paths 20 to31, 50 to 59 in accordance with predetermined kinematic laws. Thedirections of travel of the belts 2, 5 are indicated respectively by thearrows F2, F5 in FIGS. 2 to 4.

The closed paths 20 to 31, 50 to 59 are external to each other andadjacent to each other in a pinching zone in which the moving beltsections numbered 23 and 53 in FIGS. 2 to 5 are located against eachother so as to pinch the web 4 between them. The web 4 is shown as adotted line in FIG. 4 but is not illustrated in FIGS. 2 and 3 in orderto show the superposed arrangement of the belt sections 23, 53.

The adjacent horizontal sections 23, 53 of the closed paths followed bythe two belts 2, 5 in the pinching zone are delimited at the entrance ofthe pinching zone by guide rollers 35, 61 carried by the input carriage10 and, at the exit of the pinching zone, by guide rollers 38, 64carried by the output carriage 14.

The main carriages 10, 14 are located above the apron 8 and are capableof displacement in reciprocating translational motion in a horizontaldirection perpendicular to the axes of the rollers 32 to 43, 60 to 69.

The input carriage 10 (as also shown in the more detailed view of FIG.5) carries two guide rollers 34, 35 for the front belt 2 and located onthe inside of its closed path 20 to 31. Upstream of the input carriage10, the front belt 2 which carries the web 4 follows the substantiallyhorizontal section 21 which comes from the front side 7. As it reachesthe input carriage 10, the front belt 2 makes a first turn around theguide roller 34 through an angle A which is within the range of 0 to 90degrees and is oriented downwards in order to form the sloping section22, then makes a second turn around the roller 35 through an angle Bwithin the range of 90 to 180 degrees so as to constitute the horizontalsection 23 of the pinching zone, said horizontal section being directedtowards the front side 7 of the spreading and lap-forming machine. Thetotal angular deviation A+B of the front belt 2 about the guide rollers34, 35 carried by the input carriage 10 is equal to 180 degrees.

The input carriage 10 carries in addition four guide rollers 60, 61, 62,63 associated with the rear conveyor-belt 5, the rollers 60, 61 and 63being internal to its closed path 50 to 59 and the roller 62 of largerradius, or so-called detour roller, being external to said closed path50 to 59. Upstream of the input carriage 10, the rear belt 5, which doesnot carry the web 4, follows the substantially horizontal section 59which comes from the rear side 9. As it reaches the input carriage 10,the rear belt 5 makes a first turn around the guide roller 60 through anangle C which is within the range of 0 to 90 degrees and is orienteddownwards so as to pass into the section 50, then makes a second turnthrough 180 degrees around the roller 61 so as to pass into the section51, then makes a third turn around the detour roller 62 through anegative angle greater than 180 degrees (since the detour roller 62 isexternal to the closed path 50 to 59) and finally makes a fourth turnaround the roller 63 in order to pass into the horizontal section 53 ofthe pinching zone, said horizontal section being directed towards thefront side 7 of the spreading and lap-forming unit. The total angulardeviation of the rear belt 5 about the guide rollers 60, 61, 62, 63carried by the input carriage 10 is zero.

It is apparent from FIG. 5 that the two conveyor-belts 2, 5 as well asthe web 4 which passes between them are pinched along a pinching linedefined between the two rollers 35, 61 and constituting the entrance ofthe pinching zone. The respective axes of these two pinching rollers 35,61 are located in the same horizontal plane P. As it passes around theroller 63 located on the input carriage 10 beneath the horizontal planeP, the rear belt 5 is supported and meets the front belt 2 tangentiallyin the pinching zone 23, 53. The web 4 engages in the pinching zone 23,53 after having been conveyed on the sections 20, 21, 22 of the path ofthe front belt 2 and after having passed between the belts 2, 5 whichare pinched between the rollers 35, 61 along the pinching line. Thesepinching rollers 35, 61 can be thrust resiliently towards each other byknown restoring means (not shown in the drawings).

The input carriage 10 has two side-plates 11 located on each side of therollers 34, 35, 60, 61, 62, 63 which it carries. The ends of therespective shafts of said rollers 34, 35, 60, 61, 62, 63 are fixed onthe side-plates 11. On the faces remote from the rollers 34, 35, 60, 61,62, 63, the side-plates 11 of the input carriage 10 carry wheels 13which are capable of pivoting about a horizontal axis and are placed ona horizontal lateral ramp 12 rigidly fixed to the frame 1 of thespreading and lap-forming machine so as to guide the input carriage 10in its movement of translation. A similar structure which is visible inFIG. 8 is provided for guiding the output carriage 14 in its movement oftranslation.

At the exit of the pinching zone 23, 53, the two belts 2, 5 pass betweentwo delivery pinching rollers 38, 64 carried by the output carriage 14(as shown in FIGS. 2 to 4 and 8). The respective shafts of these twodelivery rollers 38, 64 are in the same horizontal plane located abovethe apron 8.

Around the pinching roller 64, the rear belt 5 turns through an angle of180 degrees in order to pass from the horizontal section 53 which formspart of the pinching zone to a horizontal section 54 which extendsimmediately above the apron 8. Said horizontal section 54 passes beneaththe input carriage 10 so as to meet a guide roller 65 having astationary shaft and located on the rear side 9 of the spreading andlap-forming unit.

In addition to the pinching roller 38, the output carriage 14 carriestwo guide rollers 36, 37 (FIG. 8) associated with the front belt 2. Atthat end of the horizontal section 23 which forms part of the pinchingzone, the front belt 2 makes a first turn around the guide roller 36through an angle which is within the range of 0 to 30 degrees and isoriented upwards in order to pass into the section 24, then makes asecond turn around the detour roller 37 located outside its closed path20 to 31 and through a negative angle greater than 180 degrees so as topass into the horizontal section 25, and finally makes a third turnthrough 180 degrees around the pinching roller 38 in order to pass intothe horizontal section 26 which extends immediately above the apron 8and then to meet a stationary-shaft guide roller 39 located on the frontside 7 of the spreading and lap-forming unit. The total deviation of thefront belt 2 around the guide rollers 36, 37, 38 carried by the outputcarriage 14 is zero.

The auxiliary carriages 16, 18 are capable of displacement intranslational motion in a horizontal direction perpendicular to the axesof the rollers 32 to 43, 60 to 69. The auxiliary carriages 16, 18 arelocated in a bottom passageway 70 which extends beneath the apron 8, ata distance from the zones in which the web 4 and the formed lap 6 pass.The bottom passageway 70 is separated from the apron 8 by a horizontalpartition-wall 72.

The auxiliary carriage 16 is designed to maintain constant the length ofthe closed path 20 to 31 which is followed by the front belt 2. Saidauxiliary carriage is adapted to carry a guide roller 41 about which thefront belt 2 performs a 180-degree turn. The front belt 2 is guidedbetween the main carriages 10, 14 and the auxiliary carriage 16 bystationary-shaft guide rollers 32, 33, 39, 40, 42, 43 located on thefront side 7 of the spreading and lap-forming unit.

The auxiliary carriage 18 is designed to maintain constant the length ofthe closed path 50 to 59 followed by the rear belt 5. Said auxiliarycarriage is adapted to carry a guide roller 67 about which the rear belt5 performs a 180-degree turn. The rear belt 5 is guided between the maincarriages 10, 14 and the auxiliary carriage 18 by stationary-shaft guiderollers 65, 66, 68, 69 located on the rear side 9 of the spreading andlap-forming unit.

As shown in FIGS. 6 and 7, each auxiliary carriage 16, 18 has twoside-plates 74, 78 located on each side of the roller 41, 67 which iscarried by said carriage. The shaft ends of each roller 41, 67 aresupported on the side-plates 74, 78 of the respective auxiliary carriage16, 18. On the faces remote from the roller 41, 67, the side-plates 74,78 carry wheels 75, 79 which are capable of pivoting about a horizontalaxis and roll on horizontal side rails 76, 80 which are rigidly fixed tothe frame 1 of the spreading and lap-forming machine in order to guidethe auxiliary carriages 16, 18 in their movements of translation. Theside rails 76, 80 extend within the bottom passageway 70 on each side ofthe rollers 41, 67. As is apparent from the partial view of FIG. 7, theyare located at different heights. In the example shown in the figures,the bottom rails 76 support the auxiliary carriage 16 which guides thefront belt 2 and the top rails 80 support the auxiliary carriage 18which guides the rear belt 5. Above the wheels 79 of the carriage 18placed on the top rails 80 extend lateral angle-iron members 82 whichare rigidly fixed to the frame 1 and form a support for thepartition-wall 72 which delimits the top portion of the passageway 70.

In order to impart motion to the main carriages 10, 14 and auxiliarycarriages 16, 18, the spreading and lap-forming machine includes drivingpinions 85, 89 driven in rotation by means (not shown) and disposedrespectively in meshing engagement with toothed drive-belts 84, 88represented schematically in dashed lines in FIGS. 2 to 4.

Two toothed drive-belts 84 extend on each side of the rollers and of theconveyor-belts between the input carriage 10 and the auxiliary carriage16, via the rear side 9 of the spreading and lap-forming unit. Betweenthe carriages 10 and 16 to which they are attached at the ends thereof,the toothed drive-belts 84 each pass around two guide pinions 85, 86(including the driving pinion 85) which pivot respectively about astationary shaft parallel to the axes of the rollers 32 to 43, 60 to 69.The pinions 85, 86 are so arranged that the end sections of the tootheddrive-belts 84 are parallel to the direction of translational motion ofthe carriages 10, 16 to which they are attached respectively.

Similarly, two toothed drive-belts 88 extend on each side of the rollersand of the conveyor-belts between the output carriage 14 and theauxiliary carriage 18, via the front side 7 of the spreading andlap-forming unit. Between the carriages 14 and 18 to which they areattached at the ends thereof, the toothed drive-belts 88 each passaround two guide pinions 89, 90 (including the driving pinion 89) whichpivot respectively about a stationary shaft parallel to the axes of therollers 32 to 43, 60 to 69. The pinions 89, 90 are so arranged that theend sections of the toothed drive-belts 88 are parallel to the directionof translational motion of the carriages 14, 18 to which they areattached respectively.

Moreover, the main carriages 10, 14 and auxiliary carriages 16, 18 arecoupled in pairs 10, 16 and 14, 18 by means of cables 92, 96 representedschematically by chain-dotted lines in FIGS. 2 to 4. These cables 92, 96are less extensible than the conveyor-belts 2, 5.

Two cables 92 extend on each side of the rollers and of theconveyor-belts between the input carriage 10 and its associatedauxiliary carriage 16, via the front side 7 of the spreading andlap-forming unit. Between the carriages 10 and 16 to which their endsare attached, the cables 92 each pass around two guide pulleys 93, 94which pivot respectively about a stationary shaft parallel to the axesof the rollers 32 to 43, 60 to 69. The pulleys 93, 94 are so arrangedthat the end sections of the cables 92 are parallel to the direction oftranslational motion of the carriages 10, 16 to which they are attachedrespectively.

Two cables 96 extend on each side of the rollers and of theconveyor-belts between the output carriage 14 and its associatedauxiliary carriage 18, via the rear side 9 of the spreading andlap-forming unit. Between the carriages 14 and 18 to which their endsare attached, the cables 96 each pass around two guide pulleys 97, 98which pivot respectively about a stationary shaft parallel to the axesof the rollers 32 to 43, 60 to 69. The pulleys 97, 98 are so arrangedthat the end sections of the cables 96 are parallel to the direction oftranslational motion of the carriages 14, 18 to which they are attachedrespectively.

During operation, the displacement of the conveyor-belts 2, 5 iscontrolled by means of the driving rollers 39, 65 and the displacementof the carriages 10, 14, 16, 18 is controlled by means of the drivingpinions 85, 89 which engage with the toothed drive-belts 84, 88.Synchronous reciprocating movements of translation are thus imparted tothe carriages 10, 14, 16, 18. The kinematic laws to be applied to themain carriages 10, 14 can for example be those taught by patent documentFR-B-2,234,395.

The end positions of the reciprocating movements are showndiagrammatically in FIGS. 2 and 3 and an intermediate position is shownin FIG. 4.

If L designates the width of the formed lap 6, the output carriage 14and its associated auxiliary carriage 18 carry out reciprocatingmovements of amplitude L at instantaneous velocities having the samevalues and in opposite directions, with the result that the length ofthe closed path 50 to 59 followed by the rear conveyor-belt 5 ismaintained constant. The input carriage 10 and its associated auxiliarycarriage 16 carry out reciprocating movements having an amplitude of theorder of L/2 at instantaneous velocities having the same values and inopposite directions, with the result that the length of the closed path20 to 31 followed by the front conveyor-belt 2 is maintained constant.

These kinematic relationships between associated carriages are obtainedby means of the cables 92, 96 which couple them together. In a firststage of the reciprocating movement from the position illustrated inFIG. 2 to the position illustrated in FIG. 3, the driving pinions 85, 89are driven in the direction indicated by the arrows G in FIG. 2. Thetoothed drive-belts 84 then pull the input carriage 10 towards the rearside 9 and the toothed drive-belts 88 pull the auxiliary carriage 18towards the front side 7. A tractive force towards the front side 7 istransmitted to the auxiliary carriage 16 by means of the cable 92 whichcouples it to the input carriage 10. A tractive force towards the rearside 9 is transmitted to the output carriage 14 by means of the cable 96which couples it to the auxiliary carriage 18.

Symmetrically, in the second stage of the reciprocating movement fromthe position illustrated in FIG. 3 to the position illustrated in FIG.2, the driving pinions 85, 89 are driven in the direction indicated bythe arrows H in FIG. 3. The toothed drive-belts 84 then pull theauxiliary carriage 16 towards the rear side 9 and the tootheddrive-belts 88 pull the output carriage 14 towards the front side 7. Atractive force towards the front side 7 is transmitted to the inputcarriage 10 by means of the cable 92 which couples it to the auxiliarycarriage 16. A tractive force towards the rear side 9 is transmitted tothe auxiliary carriage 18 by means of the cable 96 which couples it tothe output carriage 14.

The above-mentioned tractive forces, which are useful for synchronizingthe movements of the associated carriages, are advantageously absorbedby the cables 92, 96 since these latter are less extensible than theconveyor-belts 2, 5. This offers a great advantage in comparison withspreading and lap-forming devices of the prior art in which thesetractive forces are essentially absorbed by the conveyor-belts. Inconsequence, the conveyor-belts are less subjected to stress and can beof lighter construction while having improved durability. The lightconstruction of the conveyor-belts is very advantageous since it reducesthe inertia of the machine and facilitates the motion in the curvedregions of their closed paths, thus improving the regularity of transferof the web 4 in these regions.

The web 4 delivered by the card is deposited on the inclined section 20which is followed by the front conveyor-belt 2 (as shown in FIG. 4).After deviation on the roller 33, the web is conveyed horizontally onthe section 21 up to the input carriage 10. On this carriage, the web 4is first deviated by the roller 34 at an angle A ranging in value from 0to 90 degrees. The moderate value of the angle A prevents anydisturbance of the web when it is deviated by the roller 34. Afterhaving been conveyed on the inclined section 22 of the frontconveyor-belt 2, the web 4 passes around the pinching roller 35. Thepinching line defined between the rollers 35, 61 prevents any detachmentof the web 4 from the front conveyor-belt under the action ofcentrifugal force. Since the web 4 describes a curve around the pinchingroller 35 through an angle B=180°-A within the range of 90 to 180degrees and since the pinching line is located in an intermediateangular position along said curve, pinching between the rollers 35, 61does not cause any disturbances in the inclined section 22 whichprecedes this pinching action.

In the event that the angle B is too large (180 degrees or more),undesirable detachments of the web immediately upstream of the pinchingroller 35 could be observed at high rates of transfer as a result ofexcessive angular deviation or of a certain sag of the frontconveyor-belt 2 upstream of the pinching roller 35. In the event thatthe angle B is too small (90 degrees or less), the web 4 would not beconveyed in a reliable manner on the excessively inclined section 22which precedes the pinching roller 35. Preliminary pinching of the web 4between the rollers 35, 61 and the suitable value of the angle B thusensure the highest stability of transfer of the web, thus resulting in alap 6 of optimum quality.

In the example of construction described, the roller 34 which deviatesthe web 4 through the angle A upstream of the pinching line is mountedon the input carriage 10. It will be understood that the roller 34 couldhave a stationary shaft with respect to the frame 1 of the spreading andlap-forming machine. In this case, the angles A and B are variable butthe input carriage is lighter in weight and the roller 34 has the effectof supporting the conveyor-belt 2 upstream of the input carriage.

After having passed through the pinching zone 23, 53, the web 4 reachesthe output carriage 14 which deposits it in alternate folds on the apron8 so as to form the lap 6.

The formed lap 6 is sheltered to a certain extent from the air currentsproduced by the reciprocating movements of the carriages 10, 14, 16, 18by virtue of the presence of the conveyor-belt sections 26, 54 locatedimmediately above the apron 8. The presence of the vertical sections 27,55 adjacent to these sections 26, 54 has the further effect ofpreventing lateral air currents from reaching the level of the formedlap 6. Since the auxiliary carriages 16, 18 move within the bottompassageway 70 of the spreading and lap-forming unit which is separatedfrom the apron 8 by the partition-wall 72, the air currents produced bytheir movements remain essentially confined to the interior of thebottom passageway 70 at a distance from the zones in which the web 4 andthe lap 6 pass. In consequence, neither the web 4 nor the lap 6 aredisturbed by these air currents and homogeneity of the formed lap 6 isimproved, in particular when the spreading and lap-forming unit operatesat high speed.

Although, within the general scope of the invention, the auxiliarycarriages can be located in separate and distinct bottom passageways, itis advantageous for the purpose of reducing the overall size to providea single bottom passageway 70 in which the two auxiliary carriages 16,18 move. Since the auxiliary carriages 16, 18 are placed on rails 76, 80located at different heights within the bottom passageway 70, thedrive-belts 84, 88 and the coupling cables 92, 96 are also placed atdifferent heights and do not interfere with each other during operation.

The bottom passageway 70 has a length at least equal to 3L/2 or in otherwords to the sum of amplitudes of the reciprocating movements of themain carriages 10, 14 (or of the auxiliary carriages 16, 18).

It is of course possible to consider a number of different alternativesto the example of construction described in the foregoing whileremaining within the scope of the present invention.

What is claimed is:
 1. A spreading and lap-forming machine forconverting a web (4) to a lap (6) by folding in pleats, comprising atleast two conveyor-belts (2, 5) following separate closed paths (20 to31, 50 to 59) and associated with rollers (32 to 43, 60 to 69) forrespective guiding and displacement of said conveyor-belts, the closedpaths (20 to 31, 50 to 59) being external to each other and adjacent toeach other in a pinching zone (23, 53) delimited by guide rollerscarried by two main carriages (10, 14) displaceable in translationalmotion in a horizontal direction at right angles to axes of the rollers(32 to 43, 60 to 69), compensating means including at least oneauxiliary carriage (16, 18) displaceable in translational motion atright angles to the axes of the rollers (32 to 43, 60 to 69) so as tomaintain the length of each closed path (20 to 31, 50 to 59) at asubstantially constant value, each closed path (20 to 31, 50 to 59)making a 180-degree turn around at least one guide roller (41, 67)carried by said at least one auxiliary carriage (16, 18), means (20, 21,22) for transporting the web (4) to the pinching zone (23, 53), an apron(8) movable in a direction parallel to the axes of the rollers (32 to43, 60 to 69) and receives the web (4) as the web passes out of thepinching zone (23, 53), and driving means (84, 85, 88, 89) for applyingreciprocating movements of translation to the main carriages (10, 14)and to the compensating means (16, 18), wherein each said at least oneauxiliary carriage (16, 18) is located within a bottom passageway (70)which extends beneath the apron (8) and is separated therefrom by apartition-wall (72) whereby air currents generated in particular by theauxiliary carriages are prevented from propagating to the lap which isbeing formed.
 2. A spreading and lap-forming machine according to claim1, wherein the compensating means comprise a plurality of auxiliarycarriages (16, 18) associated respectively with one of the closed paths(20 to 31, 50 to 59) and located within the bottom passageway (70).
 3. Aspreading and lap-forming machine according to claim 2, wherein theauxiliary carriages (16, 18) are slidably mounted respectively on siderails (76, 80) extending within the bottom passageway (70) on each sideof said at least one roller (41, 67) which are carried by the auxiliarycarriages (16, 18), said rails (76, 80) being at different heights.
 4. Aspreading and lap-forming machine according to claim 2, wherein thebottom passageway (70) has a length at least equal to sum (3L/2) of theamplitudes of the reciprocating movements of the two main carriages (10,14), where L designates a width of the formed lap (6).
 5. A spreadingand lap-forming machine according to claim 1, wherein each main carriage(10, 14) is connected to an auxiliary carriage (16, 18) by couplingmeans (92, 96) which are less extensible than the conveyor-belts (2, 5)and so arranged as to be put under tension under action of the drivingmeans (84, 85, 88, 89).
 6. A spreading and lap-forming machine accordingto claim 1, wherein the driving means include at least onemotion-transmission element (84, 88) engageable with a driving pinion(85, 89), said motion-transmission element (84, 88) attached at one endto a main carriage (10, 14) and at another end to said at least oneauxiliary carriage (16, 18), said main carriage (10, 14) and saidauxiliary carriage (16, 18) being also connected together by thecoupling means (92, 96), the rotation of the driving pinion (85, 89) inone direction pulling the main carriage (10, 14) in a first stage ofreciprocating motion and the rotation of the driving pinion (85, 89) inthe other direction to pulling the auxiliary carriage (16, 18) in asecond stage of the reciprocating motion.